I witnessed such an incident at Walden Pond (yes, THAT Walden Pond). A guy was about to load his canoe onto his new minivan and left his young son inside (mistake #1). The kid climbed from the passenger's side to the driver's side, apparently hitting the shift lever in the process. The van began rolling down the boat ramp, accompanied by the kid screaming and a loud clicking sound of the tranny lock trying to re-engage. The guy jumped in, but he didn't know where the emergency brake was (mistake #2) and the van went in up to the base of the windshield before he could get it stopped. Driver and child exited safely, then we stood around and watched as the lights, turn signals, horn and wipers put on a show for us.